Can inspection device

ABSTRACT

A can inspection device includes a rotation device rotating cans, an imaging device taking images of rotating cans, and an image processor processing taken images. The imaging device includes a first camera taking an image of an entire can and a second camera taking an image of an opening-side end portion of the can. The image processor includes an image inspection means for inspecting whether printing is performed properly as compared with a master image by using the image taken by the first camera, a density measurement means for measuring densities in designated positions for respective colors by using the image taken by the first camera, and a printing misalignment value measurement means for measuring misalignment values with respect to set positions of printing misalignment inspection marks printed on the opening-side end portion of the can for respective colors by using the image taken by the second camera.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of the U.S. patentapplication Ser. No. 15/024,034 filed Mar. 23, 2016, which is a U.S.National Stage application of International Application No.PCT/JP2014/075021, filed Sep. 22, 2014, which claims priority under 35U.S.C. § 119 to Japanese Patent Application No. 2013-196878, filed Sep.24, 2013, Japanese Patent Application No. 2013-196880, filed Sep. 24,2013, and Japanese Patent Application No. 2013-196884, filed Sep. 24,2013. The contents of these applications are incorporated herein byreference in their entirety.

TECHNICAL FIELD

The present invention relates to a can inspection device.

BACKGROUND ART

As a printer for cans, there has been known one which includes a cansupply means for supplying cans, plural ink supply means for supplyingink for respective colors, plural plate cylinders provided so as tocorrespond to respective ink supply means, to which ink supplied fromthe ink supply means is applied and a blanket transferring ink to canssupplied from the can supply means after the ink is sequentiallytransferred from respective plate cylinders (Patent Literature 1).

There is also disclosed in Patent Literature 2 an inspection deviceperforming inspections of print states of cans which includes a rotationdevice rotating cans, an imaging device taking images of rotating cansand an image processor processing the taken images.

In Patent Literature 2, the image processor has an image inspectionmeans for inspecting whether printing is performed properly as comparedwith a master image, in which a lack of printing, a stain in appearanceand so on are inspected by the image inspection means.

CITATION LIST Patent Literature

Patent Literature 1: JP-A-2001-129968

Patent Literature 2: JP-A-5-126762

SUMMARY OF INVENTION Technical Problem

The above related-art printer for cans and the can inspection device arerespectively used as independent devices, and inspection resultsobtained in the can inspection device are not reflected on the controlof the printer.

In the inspections by the can inspection device, it is possible toperform an inspection for determining whether the product is good or badin appearance, however, the density and printing misalignment have notbeen inspected, which are necessary for improving printing accuracy ofthe printer. Accordingly, concerning defects in density, an operatorchanges an ink supply amount in the printer after a defective product isfound by a visual inspection, therefore, there is a problem thatmeasures for defects in density are delayed and many defective productsare manufactured. Similarly, concerning defects in printingmisalignment, an operator performs registration in the printer after adefective product is found by a visual inspection, therefore, there is aproblem that measures for defects in printing misalignment are delayedand many defective products are manufactured.

An object of the present invention is to provide a can inspection devicecapable of measuring densities and printing misalignment valuesnecessary for improving printing accuracy of a printer.

Solution to Problem

According to an embodiment of the present invention, there is provided acan inspection device including a rotation device rotating cans, animaging device taking images of rotating cans, and an image processorprocessing taken images, which is provided in a can printing apparatus,performing inspections of print states of the cans and feeding backinspection results to the can printing apparatus, in which the imagingdevice includes a first camera taking an image of the entire can and asecond camera taking an image of an opening-side end portion of the can,the image processor includes an image inspection means for inspectingwhether printing is performed properly as compared with a master imageby using the image taken by the first camera, a density measurementmeans for measuring densities in designated positions for respectivecolors by using the image taken by the first camera, and a printingmisalignment value measurement means for measuring misalignment valueswith respect to set positions of printing misalignment inspection marksprinted on the opening-side end portion of the can for respective colorsby using the image taken by the second camera.

The first camera is one which has been used from the past for inspectingimages, and image inspection and density measurement can be performed byusing the first camera. The second camera takes only images ofopening-side end portions of cans.

In the inspection by the image inspection means, the master image andthe taken image are compared pixel by pixel, and a partial lack, a staindue to ink scattering and so on in the image are inspected.

In the inspection by the density measurement means, densities indesignated places (density measurement places) for respective colors aremeasured. The density measurement results are fed back to the printer,thereby correcting densities before a defective product in density isfound. Accordingly, better print states can be maintained.

The printing misalignment inspection marks are printed on theopening-side end portion of the can for respective colors, an image ofwhich is taken by the second camera, and printing misalignment valuesare calculated by the printing misalignment value measurement means. Theprinting misalignment value measurement results are fed back to theprinter, thereby correcting (registration) the printing misalignmentvalues (positional deviations of plate cylinders of the printer) beforea defective product in printing misalignment is found and maintainingbetter print states.

It is preferable that the rotation device includes a vertical drive siderotating shaft driven by a motor, a vertical driven side rotating shaftrotating integrally with the drive side rotating shaft, a cylindricalholding member attached concentrically to the driven side rotating shaftso as to hold a can and an encoder detecting a rotation of the driveside rotating shaft, and the drive side rotating shaft and the drivenside rotating shaft face each other in the axial direction in a state ofbeing positioned in a vertical direction, and magnets applyingattracting forces to each other are provided to a lower end portion ofthe drive side rotating shaft and an upper end portion of the drivenside rotating shaft, thereby allowing the drive side rotating shaft andthe driven side rotating shaft to rotate integrally.

When taking images, the rotation device which can accurately turn thecan once is necessary. In the rotation device, the drive side rotationshaft and the driven side rotation shaft are integrally rotated byattracting forces of the magnets, thereby turning the can onceaccurately. Though a slight gap may exist between the drive siderotation shaft and the driven side rotation shaft, it is preferable nogap exists for increasing the attracting forces.

Advantageous Effects of Invention

When adopting the can inspection device according to the presentinvention, densities and printing misalignment values which have notbeen able to be measured can be measured. Therefore, printing accuracycan be improved by reflecting the measurement results on printingconditions of the printer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a can printing apparatus according toan embodiment of the present invention.

FIG. 2 is a view schematically showing an outline structure of a caninspection device.

FIG. 3 is a side view showing a printer.

FIG. 4 is an enlarged side view of a main part of the printer.

FIG. 5 is a schematic side view of a main part of an ink supply deviceof the printer.

FIG. 6 is a partially cutaway plan view of an ink transfer roller unitof FIG. 5.

FIG. 7 is a horizontal cross-sectional view of FIG. 6.

FIG. 8 is a vertical cross-sectional view of a registration device ofthe printer, which is the cross-sectional view taken along VIII-VIIIline of FIG. 4.

FIG. 9 is a front view of the can inspection device.

FIG. 10 is side view of FIG. 9.

FIG. 11 is a cross-sectional view taken along XI-XI line of FIG. 9.

FIG. 12 is a vertical cross-sectional view showing a rotation device ofthe can inspection device.

FIG. 13 is a view schematically showing a step of capturing images bythe can inspection device.

FIG. 14 is a view showing density data obtained from the can inspectiondevice.

FIGS. 15(a), (b), and (c) are views showing printing misalignment dataobtained from the can inspection device.

REFERENCE SIGNS LIST

(1) can printing apparatus

(2) printer

(3) ink supply device

(5) can inspection device

(47) plate cylinder

(47 a) plate cylinder shaft

(51) rotation device

(52) imaging device

(53) image processor

(54) image inspection means

(55) density measurement means

(56) printing misalignment value measurement means

(74) driven side rotating shaft

(75) holding member

(77) drive side rotating shaft

(78) motor

(77) (78) magnets

(79) first camera

(80) second camera

(96) axial direction moving means

(97) circumferential direction moving means

(98) axial direction drive means

(99) circumferential direction drive means

(101) housing

(102) sleeve (axial direction moving means)

(104) spline cylinder (circumferential direction moving member

(106) helical gear

(109) first motor

(110) second motor

(111) outer side rotation shaft (first rotation shaft)

(111 a) male screw portion

(112) inner side rotation shaft (second rotation shaft)

(112 a) male screw portion

(119) first female screw member

(120) second female screw member

(124) first motor controller

(125) second motor controller

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be explained withreference to the drawings.

FIG. 1 shows a can printing apparatus (1) according to an embodiment ofthe present invention. The can printing apparatus (1) includes a printer(2) performing printing to cans (C), a drier (4) drying printingsurfaces of the cans (C) after the printing, a can inspection device (5)inspecting print states of printing surfaces, an inspection resultfeedback controller (49) feeding back inspection results of the caninspection device (5) to the printer (2) and changing printingconditions of the printer (2) based on inspection results of the caninspection device (5) and a conveyance device (50) conveying the cans(C).

The printer (2) performs printing to a cylindrical can body which opensat the top (a body of a two-body can, which will be referred to merelyas a can (C)).

The cans (C) are transferred to a downstream side through the drier (4)after being printed in the printer (2). Print states of part of a largenumber of cans (C) passing through the drier (4) are inspected in thecan inspection device (5).

The conveyance device (50) includes a main line (50 a) supplying thecans (C) to the printer (2) and transferring the printed cans (C) to thedownstream side, a sampling line (50 b) transferring part of a number ofcans (C) passing through the driver (4) to the can inspection device (5)and a return line (50 c) returning the cans (C) determined as goodproducts in the can inspection device (5) to the main line (50 a).

In the can inspection device (5), as schematically shown in FIG. 2, thecan (C) is rotated by a rotation device (51), a drive side of therotation device (51) and the can (C) on the driven side are synchronizedthrough an encoder (92), and an image is taken by an imaging device(52), then, the image is processed in an image processor (53).

The can inspection device (5) is provided with an image inspection means(54), a density measurement means (55) and a printing misalignment valuemeasurement means (56) as the image processor (53) which processes thetaken images as shown in FIG. 1. Cans (C) determined as good products inthe can inspection device (5) are returned to the main line (50 a) asdescribed above, and cans (C′) determined as inspection rejectedproducts in the can inspection device (5) are discharged to aninspection rejected product storage part (57).

The density obtained in the density measurement means (55) and theprinting misalignment value obtained in the printing misalignment valuemeasurement means (56) in the can inspection device (5) are fed back tothe printer (2) by the inspection result feedback controller (49). Inthe printer (2), the ink supply amount is adjusted by a controller (34)according to the density and a plate cylinder position is adjusted by anautomatic registration device (58) according to the printingmisalignment value.

The printer (2) includes plural (eight in the drawing) plate cylinders(47) having plates for printing different colors respectively, a blanketcylinder (48) performing printing to cans by the ink being transferredfrom the plate cylinders (47), ink supply devices (3) for supplying inkto respective plate cylinders (47), the registration devices (58)performing positional adjustment (registration) of the plate cylinders(47) and a can feeding device (59) having plural can feeding rollers (59b) and can feeding chutes (59 a) as shown in FIG. 3 and FIG. 4.

The registration device (58) includes an axial direction moving means(96) for moving the plate cylinder (47) in the axial direction and acircumferential direction moving means (97) for moving the platecylinder (47) in the circumferential direction. The registration device(58) is provided with controllers (124) (125) controlling motors (109)(110) provided in respective moving means (96) (97) as shown in FIG. 4.

FIG. 5 to FIG. 7 show the ink supply device. In the followingexplanation, the right side of FIG. 5 (the lower side of FIG. 6)corresponds to the front, the left side of FIG. 5 (the upper side ofFIG. 6) correspond to the back, and left and right seen from the frontcorrespond to left and right.

As shown in FIG. 5 in an enlarged manner, an inkwell roller (41) isarranged in the ink supply device (3) so as to be close to a rear endpart of an inkwell member (40), which forms an inkwell (42), and an inkpassage (43) having a given gap between the rear end part of the inkwellmember (40) and the surface of the inkwell roller (41) is formed.

A first ink distributing roller (44) in plural ink distributing rollers(44) (46) is arranged in the rear direction of the inkwell roller (41),an ink transfer roller unit (45) is arranged between the inkwell roller(41) and the ink distributing roller (44) so as to be close to bothrollers. The roller unit (45) is an aggregation of plural (seven in thedrawing) ink transfer rollers (15) divided in the axial direction of therollers (41) (44), and these ink transfer rollers (15) are arranged atsmall intervals in the axial direction. Shafts of these rollers (15)(41) (44) are parallel to one another and extend in a right and leftdirection. The inkwell roller (41) and the ink distributing roller (44)are rotatably supported by a frame (7) of the printer, and continuouslyrotated in an arrow direction of FIG. 4 at a rotation speed synchronizedwith each other by a not-shown drive device. For example, the rotationspeed of the inkwell roller (41) is approximately 1/10 of that of theink distributing roller (44).

The details of the ink transfer roller unit (45) are shown in FIG. 6 andFIG. 7. FIG. 6 is a partially cut-out plan view of the roller unit (45),and FIG. 7 is an enlarged horizontal cross-sectional view of FIG. 6 seenfrom the left side.

Right and left both ends of a straight support member (6) which isparallel to the rollers (41) (44) are fixed by the frame (7), and pluralmovable members (8) are attached around the support member (6). Thesupport member (6) has a prismatic shape a front and rear width of whichis slightly larger than a vertical width. The movable members (8) have ashort columnar shape, and relatively large prismatic holes (9)penetrating the movable members (8) in the axial direction are formed inthe movable members (8). The plural movable members (8) are aligned inthe axial direction between a pair of short-columnar shaped fixingmembers (10) fixed to the frame (7) so as to face each other andpenetrated by the support member (6), and the support member (6)penetrates through the holes (9) of these movable members (8). Avertical width of the holes (9) of the movable members (8) isapproximately equal to the vertical width of the support member (6), andboth vertical surfaces of the holes (9) slidingly contact both verticalsurfaces of the support member (6). A front and rear width of the hole(9) is slightly larger than the front and rear width of the supportmember (6), and the movable members (8) are configured to move in thefront and rear direction with respect to the support member (6) betweena front end position where rear surfaces of the holes (9) contact a rearsurface of the support member (6) and a rear end position where frontsurfaces of the holes (9) contact a front surface of the support member(6). A rectangular groove (11) is formed over the entire length of themovable member (8) on an upper surface of the hole (9) of the movablemember (8) slidingly contacting the support member (6).

Respective movable members (8) are positioned in the axial directionwith respect to the support member (6) as described later. Small gapsare provided in the axial direction between the movable members (8)mutually and between the movable members (8) and the fixing members (10)of both ends. Accordingly, respective movable members (8) can beindividually moved in the front and rear direction with respect to thesupport member (6).

An inner ring of a ball bearing (12) as a rolling bearing is fixed to anouter periphery of each movable member (8). A metal sleeve (14) is fixedto an outer periphery of an outer ring of each ball bearing (12), andthe thick cylindrical ink transfer roller (15) made of rubber is fixedto an outer periphery of the sleeve (14).

Short columnar dust proof members (16) are fitted between mutual outerperipheries of adjacent movable members (6). The dust proof member (16)is formed of appropriate rubber-state elastic materials such as naturalrubber, synthetic rubber and synthetic resin, and flange portions (16 a)slightly protruding to the inside are integrally formed at both endsthereof. These flange portions (16 a) are fitted to annular grooves (17)formed on outer peripheral surfaces in portions close to right and leftboth ends of the movable member (8), thereby fixing the dust proofingmember (16) to the movable member (8). Similar dust-proof members (16)are fitted between mutual outer peripheries of the movable members (8)on right and left both ends and the fixing members (10) adjacent to themembers.

A roller position switching device (19) switching the position of theink transfer roller (15) as described below is provided on the supportmember (6) side between each movable member (8) and the support member(6).

A hole slightly extending in the rear direction from the front surfaceis formed in a portion of the support member (6) corresponding to thecentral portion of the movable member (8) in the axial direction tothereby form a cylinder portion (20) and to form a spring housing hole(21) slightly extending to the front direction from the rear surface.The center of the cylinder portion (20) and the center of the springhousing hole (21) are on one straight line in the front and reardirection in the vicinity of the center of the movable member (8) in thevertical direction. A short columnar piston (22) is inserted into thecylinder portion (20) so as to be slidable in the front and reardirection through an O-ring (23). A ball (24) as a biasing member isinserted into the spring housing hole (21) so as to be slidable in thefront and rear direction, and a compressed coil spring (25) biasing theball (24) backward is inserted into the spring housing hole (21).

Concave portions (26) (27) are formed on the front surface of the hole(9) of the movable member (8) facing the center of the piston (22) andthe rear surface of the hole (9) facing the center of the ball (24). Thewidth of respective concave portions (26) (27) of the movable member (8)in the axial direction is fixed. Cross-sectional shapes of respectiveconcave portions (26) (27) in a cross section orthogonal to the axisline of the movable member (8) are the same, which forms an arc shapearound a straight line parallel to the axis line. A tapered projection(22 a) is formed in the center of an end surface of the piston (22)facing the concave portion (26), and the projection (22 a) is fitted tothe concave portion (26). A length of the piston (22) excluding theprojection (22 a) is slightly shorter than a length of the cylinderportion (20), and most part of the projection (22 a) projects from thefront surface of the support member (6) even in a state where the piston(22) retreats into the cylinder portion (20) to the maximum. On theother hand, part of an outer periphery of the ball (24) is fitted to theconcave portion (27).

In a rear part of the support member (6), the ball (24) is pressurecontacted to the rear surface of the hole (9) of the movable member (8)constantly by an elastic force of a spring (25), and part of the outerperiphery of the ball (24) is fitted to the concave portion (27) to bepressure contacted to an edge of the concave portion (27) in the frontand rear direction. On the other hand, in a front part of the supportmember (6), the front surface of the support member (6) or the piston(22) is pressure contacted to the front surface of the hole (9) of themovable member (8), and most part of the projection (22 a) of the piston(22) is fitted to the concave portion (26). Most part of the projection(22 a) of the piston (22) and part of the ball (24) are fitted to theconcave portions (26) (27) constantly as described above, therebypositioning the movable member (8) in the axial direction with respectto the support member (6).

An air supply hole (28) having a circular shape in cross section, whichextends from the left end of the support member (6) in the axialdirection to be closed in the vicinity of the right end is formed in thesupport member (6). A left-end opening end of the hole (28) is connectedto a compressed air source (29) through a proper pipe.

A switching valve (solenoid valve) (30) is attached to an upper surfaceof the support member (6) facing the groove (11) of the movable member(8), and two ports of the valve (30) are respectively communicated tothe air supply hole (28) and the cylinder portion (20) throughcommunication holes (31) (32) formed in the support member (6). Anelectric wire (33) of the valve (30) is pulled out to the outsidethrough a portion of the groove (11) and is connected to the controller(34).

The cylinder portion (20) is communicated to the air supply hole (28)through the valve (30) in a state where electric current is applied(on-state) to the valve (20) and the cylinder portion (20) iscommunicated to the air through the valve (30) in a state where electriccurrent is stopped (off-state). The energized state of the valve (30) ofeach switching device (19) is individually switched by the controller(34), thereby individually switching the position of each ink transferroller (15) in the front and rear direction.

When the valve (30) is switched to the off-state, the cylinder portion(20) is communicated to the air, therefore, the piston (22) is capableof moving in the cylinder portion (20) freely. Accordingly, the movablemember (8) is moved to the rear side by the spring (25) through the ball(24). As a result, the movable member (8) and the ink transfer roller(15) are switched to the rear end position (non-transfer position), andthe ink transfer roller (15) is separated from the inkwell roller (41)and pressure contacts the ink distributing roller (44).

When the valve (30) is switched to the on-state, the cylinder portion(20) is communicated to the air supply hole (28) and communicated to thecompressed air source (29) through the air supply hole (28), therefore,compressed air is supplied to the cylinder portion (20). Accordingly,the piston (22) protrudes to the front direction from the support member(6) against the force of the spring (25), and the movable member (8) ismoved forward accordingly. As a result, the movable member (8) and theink transfer roller (15) are switched to the front end position(transfer position) and the ink transfer roller (15) is separated fromthe ink distributing roller (44) and pressure contacts to the inkwellroller (41).

A position switching detection sensor (35) including magnetic sensor isfixed in an embedded manner in a lower surface of the support member (6)slidingly contacting a bottom wall of the hole (9) of the movable member(8), and a permanent magnet (36) is fixed in an embedded manner in abottom wall of the hole (9) of the movable member (8), which faces thesensor. A lower surface of the sensor (35) is flush with the lowersurface of the support member (6) or positioned slightly inside (upperside) thereof. An upper surface of the permanent magnet (36) is flushwith the bottom wall surface of the hole (9) of the movable member (8)or positioned slightly inside (lower side) thereof. In the state wherethe movable member (8) is switched to the rear end position, the sensor(35) faces the central part of the permanent magnet (36) in the frontand rear direction. In the state where the movable member (8) isswitched to the front end position, the sensor (35) is deviated rearwardfrom the permanent magnet (36). Therefore, the output of the sensor (35)is changed according to the position of the movable member (8) and wherethe movable member (8) is, namely, the ink transfer roller (15) isrecognized according to the output of the sensor (35).

The ink in the inkwell (42) comes out to the surface of the outerperiphery of the inkwell roller (41) through the ink passage (43). Afilm thickness of the ink coming out to the surface of the inkwellroller (41) corresponds to the size of the gap of the ink passage (43),and the size of the gap of the ink passage (43) is adjusted, therebyadjusting the film thickness of the ink coming out to the surface of theinkwell roller (41). Normally, the size of the gap of the ink passage(43) is adjusted so that the film thicknesses of the ink are equivalentin all the ink transfer rollers (15). The ink coming out to the surfaceof the outer periphery of the inkwell roller (41) is transferred to theink transfer roller (15) while the ink transfer rollers (15) areswitched to the front end position. The ink transferred to respectiveink transfer rollers (15) is transferred to the ink distributing roller(44) while the ink transfer rollers (15) are switched to the rear endposition. The ink transferred to the ink distributing roller (44) issupplied to a print surface further through other plural inkdistributing rollers which are not shown. Whether the switching of theposition of the ink transfer rollers (15) is normal or not is detectedby the output of the sensor (35), and an alarm is given when the inktransfer rollers (15) are not normally switched.

In the printer (2), the ink is transferred by switching the position ofa required ink transfer roller (15) at transfer timings of givenintervals, and a rotation angle (contact rotation angle) of the inkwellroller (41) made from a contact to the inkwell roller (41) until aseparation form the inkwell roller (41) is controlled in each inktransfer roller (15) by the controller (34), thereby controlling aperipheral length of the ink transferred from the inkwell roller (41) tothe ink transfer roller (15), as a result, the amount of ink supplied tothe print surface is adjusted according to the position in the widthdirection.

The control of the contact rotation angle is performed by controlling aperiod of time (contact instruction period) from contact instruction(the output of a switching instruction to the transfer position withrespect to the ink transfer roller (15)) until non-contact instruction(the output of a switching instruction to the non-transfer position.

In the case where the density of a certain color in eight colors is low,the contact period of the color in the ink supply device (3) iselongated, and in the case where the density of a certain color is high,the contact period of the color in the ink supply device (3) isshortened, thereby controlling the density.

FIG. 8 shows the registration device (58) of the printer (2). In theexplanation of the registration device (58), top/bottom and right/leftcorrespond to top/bottom and right/left in FIG. 8.

As shown in FIG. 8, the axial direction moving means (96) moving theplate cylinder (47) in the right and left direction (axial direction)includes a sleeve (a cylindrical axial direction moving member) (102)moving in the axial direction integrally with a plate cylinder shaft (47a). The sleeve (102) is supported by a cylindrical plate cylinder shafthousing (101) so as not to rotate and so as to move in the axialdirection. The plate cylinder shaft (47 a) is supported by the sleeve(102) through a bearing (103) so as to rotate freely and so as not tomove in the axial direction. The plate cylinder shaft (47 a), the sleeve(102) and the plate cylinder shaft housing (101) are concentricallyarranged.

The circumferential direction moving means (97) which moves the platecylinder (47) to the circumferential direction includes a splinecylinder (circumferential direction moving member) (104) fitted to aspline shaft portion (47 b) provided in a right end portion of the platecylinder shaft (47 a) extending in the right direction from the centralportion of the plate cylinder (47). An annular groove is formed in anouter periphery of the spline cylinder (104), and a helical gear (105)is fitted into the annular groove and fixed therein. The helical gear(105) is engaged with a helical gear (106) arranged so as not to move inthe axial direction. The spline cylinder (104) is attached to the splineshaft portion (47 b), namely, the plate cylinder shaft (47 a) by splinefitting so as to integrally move as well as so as to relatively move inthe axial direction. The plate cylinder shaft (47 a) moves in acircumferential direction with the movement of the spline cylinder (104)in the axial direction due to the engagement of the helical gears (105)(106) with each other.

The plate cylinder shaft housing (101) is fixed to a frame (107)orthogonal to the plate cylinder shaft housing (101). A right endportion of a motor housing (108) arranged in parallel to the platecylinder shaft housing (101) above the plate cylinder shaft housing(101) is fixed to the frame (107).

In a left end of the motor housing (108), two motors, namely, a firstmotor (109) on a lower side (side close to the plate cylinder (47)) anda second motor (110) on an upper side (side apart from the platecylinder (47)) are arranged.

In the motor housing (108), a hollow outer side rotation shaft (firstrotation shaft) (111) rotated by the first motor (109) and a solid innerside rotation shaft (second rotation shaft) (112) arrangedconcentrically with the outer side rotation shaft (111) and rotated bythe second motor (110) are arranged so as to rotate.

A drive gear (113) is attached to a right end portion of a drive shaft(109 a) extending in the right direction of the first motor (109), andthe drive gear (113) is engaged with a driven gear (114) providedintegrally with a left end portion of the outer side rotation shaft(111). A drive gear (115) is attached to a right end portion of a driveshaft (110 a) extending in the right direction of the second motor(110), and the drive gear (115) is engaged with a driven gear (116)provided integrally with a left end portion of the inner side rotationshaft (112).

The outer side rotation shaft (111) is supported by the motor housing(108) through a bearing (117) so as to rotate. The inner side rotationshaft (112) is supported by the outer side rotation shaft (111) througha bearing (118) so as to relatively rotate. Accordingly, the outer siderotation shaft (111) and the inner side rotation shaft (112) areconfigured to rotate independently.

A male screw portion (111 a) is provided in a right end portion of theouter side rotating shaft (111), and a first female screw member (119)is screwed to the male screw portion (111 a). A right end portion of theinner side rotation shaft (112) protrudes to the right direction from aright end of the outer side rotating shaft (111), and a male screwportion (112 a) is provided in the right end portion and a second femalemember (120) is screwed to the male screw portion (112 a).

Respective female screw members (119) (120) are slidably fitted to apair of guide bars (121) which are fixed to the frame (107) and extendto the right direction in parallel to the respective rotating shafts(111) (112). Accordingly, the respective female screw members (119)(120) are not able to rotate, and move in the right and left direction(axial direction of the respective rotating shafts (111) (112)) with therotation of the respective rotating shafts (111) (112).

A first coupling member (122) engaged with the sleeve (102) and couplingthe first female screw member (119) and the sleeve (102) is fixed to thefirst female screw member (119) screwed to the outer side rotating shaft(111). Accordingly, the first female screw member (119) and the sleeve(102) integrally move in the axial direction with the rotation of theouter side rotating shaft (111).

A second coupling member (123) engaged with the spline cylinder (104)and coupling the second female member (120) and the spline cylinder(104) is fixed to the second female screw member (120) screwed to theinner side rotating shaft (112). Accordingly, the second female screwmember (120) and the spline cylinder (104) integrally move in the axialdirection with the rotation of the inner side rotating shaft (112).

An axial direction drive means (98) moving the sleeve (102) as an axialdirection moving means includes the first motor (109), the outer siderotation shaft (111), the first female screw member (119) and the firstcoupling member (122).

A circumferential direction drive means (99) moving the spline cylinder(104) as a circumferential direction moving member includes the secondmotor (110), the inner side rotating shaft (112), the second femalescrew member (120) and the second coupling member (123).

The controller (124) controlling the first motor (109) adjusts an axialdirection position of the plate cylinder (47) by driving the first motor(109) in accordance with a printing misalignment value of a can (C) in aheight direction in the printing misalignment value measurement means(56) of the can inspection device (5). The controller (125) controllingthe second motor (110) adjusts a circumferential direction position ofthe plate cylinder by driving the second motor (110) in accordance witha printing misalignment value of a can (C) in a circumferentialdirection in the printing misalignment value measurement means (56).

Specific structures of mechanical portions of the can inspection device(5) according to the embodiment of the present invention are shown inFIG. 9 to FIG. 12.

The can inspection device (5) includes a loading conveyor (61)sequentially loading cans (C) for inspection, a take-out device (62)provided at an end part of the loading conveyor (61) and taking out thecans (C) for inspection from the loading conveyer (61), the can rotationdevice (51) holding the cans (C) for inspection taken out in thetake-out device (62) and rotating the cans (C), the imaging device (52)taking images of the cans (C), a controller (not shown) formed of acomputer having a CPU executing logical operation of the image processor(53), a ROM storing control programs, a RAM storing data and so on, adisplay displaying image processing results and so on, an unloadingconveyor (63) unloading cans (C) as good products and a discharge chute(64) discharging cans (C′) as inspection rejected products.

The take-out device (62) includes a suction part (65) adsorbing cans fedby the loading conveyer (61) and pushed out and a cylinder part (66)moving the suction part (65) upward. The suction part (65) has asemi-cylindrical concave portion (65 a) to which an intermediate portionof the can (C) is fitted.

The can rotation device (51) includes a main shaft (71) rotated by amotor (72) and a rotating disk (73) attached to the main shaft (71). Themotor (72) is attached to an upper surface of a top wall of a housing(70), and the main shaft (71) is rotatably supported at the top wall ofthe housing (70).

The rotating disk (73) is concentric with the main shaft (71), rotatingintegrally with the main shaft (71). In an outer periphery of therotating disk (73), plural arms (73 a) are provided so as to protrudeoutward in a radial direction at equal intervals. Vertical driven siderotating shafts (74) are supported in respective arms (73 a) of therotating disk (73) so as to rotate freely. Holding members (75) formedconcentrically with the driven side rotating shafts (74) so as to holdthe cans (C) are attached to the driven side rotating shafts (74).

The driven side rotating shafts (74) revolve around the main shaft (71)through the set position of the take-out device (62), the set positionof the imaging device (52), the set position of the unloading conveyor(63) and the set position of the discharge chute (64) with the rotationof the rotating disk (73) so as to return to the set position of thetake-out device (62).

A driving device (76) for rotating (revolving) the driven side rotatingshaft (74) is arranged above the driven side rotating shaft (74)positioned in the set position of the imaging device (52) so as to besupported on the top wall of the housing (70). The driving device (76)includes a vertical drive side rotating shaft (77) and a motor (78)provided in concentric with the drive side rotating shaft (77).

As the imaging device (52), a first camera (79) taking an image of theentire can and a second camera (80) taking an image of an opening-sideend portion of the can are used. The image taken by the first camera(79) is used in the image inspection means (54) and the densitymeasurement means (55). The image taken by the second camera (80) isused in the printing misalignment value measurement means (56).

In the set position of the imaging device (52), the drive side rotatingshaft (77) faces the driven side rotating shaft (74) in the axialdirection, and magnets (81) (82) applying attracting forces to eachother are fixed to a lower end portion of the drive side rotating shaft(77) and an upper end portion of the driven side rotating shaft (74).Accordingly, a lower surface of the magnet (81) provided in the lowerend of the drive side rotating shaft (77) and an upper surface of themagnet (82) provided on an upper end of the drive side rotating shaft(74) are adsorbed (integrated) by respective attracting forces of themagnets (81) (82).

The driven side rotating shafts (74) are supported by cylindricalcasings (83) provided in respective arms (73 a) of the rotating disk(73) so as to rotate and so as not to move in the axial direction.

As shown in FIG. 12, the drive side rotating shaft (77) includes a solidshaft portion (85) and an outer cylindrical portion (86) spline-fittedto the shaft portion (85) concentrically with the shaft portion (85). Alower end portion of the shaft portion (85) slightly protrudes downwardfrom a lower end of the outer cylindrical portion (86) and the magnet(81) is attached to the lower end portion of the shaft portion (85). Anupper part of the shaft portion (85) protrudes upward as compared withan upper end of the outer cylindrical portion (86), and a rotary encoder(60) detecting a rotation speed (rotation angle) of the drive siderotating shaft (77) is attached to an upper end of the shaft portion(85) through a coupling (95).

A male screw is formed on an outer periphery of the outer cylindricalportion (86), and a screw (87) screwed to a lower portion of the outercylindrical portion (86) and a screw (88) screwed to an upper portion ofthe outer cylindrical portion (86) sandwich a motor rotor (76 a)arranged on an outer periphery of the outer cylindrical portion (86)from upper and lower sides, therefore, the outer cylindrical portion(86) rotates integrally with the motor rotor (76 a). The shaft portion(85) spline-fitted to the outer cylindrical portion (86) integrallyrotates accordingly. The shaft portion (85) can relatively move in theaxial direction with respect to the outer cylindrical portion (86).

The driven side rotating shaft (74) is supported by the casing (83)through a bearing (84). The drive side rotating shaft (77) and thedriven side rotating shaft (74) are coupled (adsorbed) by the attractingforces of the magnets (81) (82), and the driven side rotating shaft (74)rotates integrally with the rotation of the driven side rotating shaft(74).

Annular spring brackets (89) (90) are fixed to an upper end portion ofthe shaft portion (85) of the drive side rotating shaft (77) and anupper end portion of the outer cylindrical portion (86), and acompressed coil spring (91) is arranged between both spring brackets(89) (90). Therefore, when the shaft portion (85) moves downward, thecompressed coil spring (91) is further compressed and biases the shaftportion (85) upward, which prevents the shaft portion (85) from movingdownward. Accordingly, the magnets (81) (82) applying attracting forcesto each other do not contact each other, which prevents abrasion betweenthe magnets (81) (82).

The drive side rotating shaft (77) rotates by being driven by the motor(78), and the can (C) held by the driven side rotating shaft (74)rotates with the rotation, and an image of one rotation is captured byimaging device (52). At this time, a period for one pixel is determinedso as to correspond to an output of the rotary encoder (60) foreliminating an error.

The rotation of the can (C) and the rotation of the rotary encoder (60)(rotation of the drive side rotating shaft (77)) are rotated so as to besynchronized with each other for eliminating the error. According tothis, an output (pulse) of the rotary encoder (60) and the flow of theimage for one pixel are synchronized. Even when an uneven rotationoccurs in respective cans (C) to be measured, taken images of respectivecans are not extended/contracted and stable inspections are performed.

An air vent passage (92) one end of which opens to a lower end and theother of which opens to an outer periphery in the vicinity of an upperend portion is provided in the driven side rotation shaft (74). A pipefor evacuation (93) for evacuating the air vent passage (92) is attachedto the casing (83).

The holding member (75) is made of resin and has a cylindrical shape,and a cylindrical suction chamber (94) opening downward is provided in alower end portion of the holding member (75). The air vent passage (92)of the driven side rotation shaft (74) is communicated to the suctionchamber (94). The suction chamber (94) becomes in a negative pressure(vacuum) by evacuating the suction chamber (94) by a not shown vacuumpump through the pipe for evacuation (93), and the can (C) is held bythe holding member (75).

In the imaging device (5), an image of the print surface of the can (C)is started to be taken from an arbitrary position of the can (C) in astate where the can (C) rotates at an arbitrary speed.

In printing for one turn, when a print end position abuts on a printstart position, printing of one turn is just performed. As the printingis slightly misaligned in respective cans at the abutting part betweenthe print end position and the print start position, a largemisalignment occurs when the abutting part exists at an intermediatepart in image capturing. Therefore, when a range from a designation markto a designation mark is defined as one turn, the abutting part ofprinting is included in the intermediate part, which is not desirable.Accordingly, an image for one turn from the print start position to theprint end position is captured at the time of capturing the image. Asthe designation marks, marks which can be easily found in printed imagesare used, for example, bar codes are used.

As the position of the can (C) fed to the inspection device (5) is notspecified, positions of the can (C) facing the cameras (79) (80) are atrandom. Therefore, it is necessary to find the print start position forcapturing the image for one turn. Accordingly, in an operation ofcapturing the image, as distances (angles) from a designation mark (M)to print start positions (S1) (S2) are previously known in FIG. 13,first, the designation mark (M) should be found, and after thedesignation mark (M) is found, a position obtained by moving in areverse direction by “a” as a distance corresponding to the angle isdetermined as the print start position (S1), namely, the image capturingstart position. It is also possible to determine a position obtained bymoving in a positive direction by “b” as the print start position (S2),namely, the image capturing start position. Accordingly, it is possibleto capture an image of just one turn from the print start position(S1)/(S2) to the print end position (E1)/(E2) which is shown by “L1” or“L2”.

The image inspection by the image inspection means (54) of theinspection device (5) has been hitherto performed, in which a masterimage and a taken image are compared pixel by pixel by the imageinspection means (54) to thereby perform inspections for a partial lack,a stain due to ink scattering and so on in the image. In the imageinspection means (54), a product having a lack with a size exceeding apredetermined size is determined as an inspection rejected product, anda product exceeding a misalignment allowable value with respect to themaster image is also determined as an inspection rejected product.

The inspection by the density measurement means (55) of the inspectiondevice (5) is performed with respect to single-color solid portions.That is, as it is difficult to measure the density at a place whereplural colors overlap, therefore, places where the single-color solidportions exist are designated in advance for respective colors, anddensities in the designated places (density measuring places) aremeasured. A density value may be calculated as an arithmetic mean valueof RGB components of pixels defined as the density measurement place,and can be obtained as a density difference between the density at eachplace and the density of the master image. In the case where thesingle-color solid portion has, for example, a size of 0.8 mm×0.8 mm,the density can be measured. When it is difficult to measure the densityaccurately because the size is not able to be secured or other reasons,whether the density difference with respect to the master image iswithin a reference or not is just determined. Densities corresponding tothe number (seven) of ink transfer rollers (15) can be obtained for onecolor as shown in FIG. 14. As the number of colors (the number of platecylinders) is eight in the embodiment, density measurement values of 8×7can be obtained. The density measurement results shown in FIG. 14 aredisplayed on the display of the inspection device (5).

The density measurement results are fed back to the printer (2) by theinspection result feedback controller (49) without human intervention,and thus, positions of respective ink transfer rollers (15) arecontrolled by the controller (34) of the ink supply devices (3) tochange the amount of ink to be supplied. Accordingly, a good print statecan be maintained in the printer (2) by correcting densities before adefective product in density is found.

The image inspection means (54) and the density measurement means (55)are executed by using the image of the entire can taken by the firstcamera (79), however, the printing misalignment value measurement means(56) are executed by using the image taken by the second camera (80)taking an image of an opening-side end portion of the can.

The opening-side end portion of the can (C) is a portion covered with alid, which is a portion where printing has not been performed and whereinspection has not been required in related-art cans. Concerning cans(C) to be inspected by the inspection device (5) according to theembodiment, printing misalignment value inspection marks are printed forrespective colors on the opening-side end portion of the can (C). Thatis, as shown in FIG. 15(a), the printing misalignment value inspectionmarks shown by “A” are added on the print surface of the can (C) inaddition to previously existing items such as a product name, a companyname, ingredients and a bar code.

The printing misalignment value inspection marks (A) are provided forthe total eight colors from one to eight as shown in FIG. 15(b) in anenlarged manner. Positions shown by solid lines in the drawing arereference positions (positions of designation marks in the masterimage), and positions shown by two-dot chain lines in the drawing arepositions of respective colors obtained from the taken image. Accordingto the drawing, it is found that, for example, printing misalignment isextremely small in a color of No. 7, a printing misalignment value inthe height direction of the can (C) is large in a color of No. 3, and aprinting misalignment value in a circumferential direction of the can(C) is large in a color of No. 6. The printing misalignment value iscalculated as a value indicating to what degree (or how long (mm)) (asthe number of pixels) the position of the designation mark in the masterimage is deviated from the position of the designation mark in the takenimage, and calculated numerals are displayed on the display of theinspection device (5) as shown in FIG. 15(c). The misalignment amountsare calculated in the height direction of the can (axial direction ofthe plate cylinder (47)) and in the circumferential direction of the can(circumferential direction of the plate cylinder (47)) respectively. Theprinting misalignment measurement results are fed back to the printer(2) by the inspection result feedback controller (49) without humanintervention. The printing misalignment measurement results may also befed back to the printer (2) not by using the inspection result feedbackcontroller (49) (may be also fed back manually).

The controller (34) of the ink supply device (3) controls the contactperiod in the ink supply device (3) based on a density target valuewhich is previously set, and the density measurement results obtained inthe density measurement means (55) of the can inspection device (5) areadded to the control. Specifically, when the density of a certain coloris lower than a target value at a certain place, a contact lengthbetween the ink transfer roller supplying the color to the place and theinkwell roller is elongated, thereby increasing the density. When thedensity of a certain color is higher than a target value at a certainplace, the contact length between the ink transfer roller supplying thecolor to the place and the inkwell roller is shortened.

In the example shown in FIG. 14, for example, the density is relativelyhigh at a place of No. 4 and is relatively low at a place of No. 7 inthe first color. In the second color, the density is relatively high ata place of No. 4 and the density is relatively low at a place of No. 2.When such density measurement results are outputted to the printer (2),in the controller (34) of the ink supply device (3) of the printer (2),for example, the contact length between the ink transfer roller of No. 4which supplies the ink to the plate cylinder of the first color and theinkwell roller is shortened, and the contact length between the inktransfer roller of No. 7 which supplies the ink to the plate cylinder ofthe first color and the inkwell roller is lengthened based on the inputof the density measurement results. Accordingly, the density of thefirst color is changed to be uniform as the whole. The same process isperformed to other colors.

The density measurement results in the can inspection device (5) are fedback to the printer (2) immediately as described above, and thepositions of respective ink transfer rollers (15) are controlled by thecontroller (34) of the ink supply devices (3) to thereby change theamount of ink to be supplied. Accordingly, the density can be correctedbefore a defective product in density is found, which can preventgeneration of the defective product in density.

The printing misalignment value of the can (C) in the height directionis fed to the controller (124) which controls the first motor (109) ofthe registration device (58), and the controller (124) drives the firstmotor (109) in accordance with the printing misalignment value, therebyautomatically adjusting the position of the plate cylinder (47) in theaxial direction. The printing misalignment value of the can (C) in thecircumferential direction is fed to the controller (125) which controlsthe second motor (110) of the registration device (58), and thecontroller (125) drives the second motor (110) in accordance with theprinting misalignment value, thereby automatically adjusting theposition of the plate cylinder (47) in the circumferential direction.

The printing misalignment value measurement results in the caninspection device (5) are immediately fed back to the printer (2) by theinspection result feedback controller (49), and the positionaladjustment (registration) of the plate cylinder (47) is performed by theregistration device (58). Accordingly, the printing misalignment valuecan be corrected before a defective product in printing misalignment isfound, which can prevent generation of the defective product in printingmisalignment.

INDUSTRIAL APPLICABILITY

When adopting the can printing apparatus according to the presentinvention, printing conditions of the printer are changed based oninspection results of the can inspection device, therefore, printingdefects are solved in an early stage, as a result, it is possible tocontribute to the improvement of printing accuracy and labor saving inthe printer.

The invention claimed is:
 1. A can inspection device comprising: an imaging device taking images of rotating cans; and an image processor processing taken images, which is provided in a can printing apparatus, performing inspections of print states of the cans and feeding back inspection results to the can printing apparatus, wherein the imaging device includes a first camera facing to an entire can from a direction orthogonal to an axial direction of the can and taking an image of the entire can and a second camera facing to an opening-side end portion of the can from a direction orthogonal to the axial direction of the can and taking an image of the opening-side end portion of the can, wherein whether printing is performed properly as compared with a master image is inspected, densities in designated positions for respective colors are measured by using the image taken by the first camera, and misalignment values with respect to set positions of printing misalignment inspection marks printed on the opening-side end portion of the can for respective colors are measured by using the image taken by the second camera, wherein the image processor is configured to: inspect whether the printing is performed properly as compared with the master image, measure densities in the designated positions for respective colors by using the image taken by the first camera, and measure the misalignment values with respect to the set positions of the printing misalignment inspection marks printed for respective colors by using the image taken by the second camera.
 2. The can inspection device according to claim 1, wherein a rotation device for rotating cans includes a vertical drive side rotating shaft driven by a motor, a vertical driven side rotating shaft rotating integrally with the drive side rotating shaft, a cylindrical holding member attached concentrically to the driven side rotating shaft so as to hold a can and an encoder detecting a rotation of the drive side rotating shaft, and the drive side rotating shaft and the driven side rotating shaft face each other in the axial direction in a state of being positioned in a vertical direction, and magnets applying attracting forces to each other are provided to a lower end portion of the drive side rotating shaft and an upper end portion of the driven side rotating shaft, thereby allowing the drive side rotating shaft and the driven side rotating shaft to rotate integrally.
 3. A can inspection system comprising: cans having printing misalignment inspection marks on an opening-side end portion thereof; and the can inspection device according to claim
 1. 4. A can inspection device comprising: a rotation device rotating cans; an imaging device taking images of rotating cans; and an image processor processing taken images, which is provided in a can printing apparatus, performing inspections of print states of the cans and feeding back inspection results to the can printing apparatus, wherein the imaging device includes a first camera taking an image of the entire can and a second camera taking an image of an opening-side end portion of the can, wherein whether printing is performed properly as compared with a master image is inspected, densities in designated positions for respective colors are measured by using the image taken by the first camera, and misalignment values with respect to set positions of printing misalignment inspection marks printed on the opening-side end portion of the can for respective colors are measured by using the image taken by the second camera, wherein the rotation device includes a vertical drive side rotating shaft driven by a motor, a vertical driven side rotating shaft rotating integrally with the drive side rotating shaft, a cylindrical holding member attached concentrically to the driven side rotating shaft so as to hold a can and an encoder detecting a rotation of the drive side rotating shaft.
 5. A can inspection device comprising: an imaging device taking images of rotating cans; an image processor processing taken images; and a conveyance device conveying cans, which is provided in a can printing apparatus, performing inspections of print states of the cans and feeding back inspection results to the can printing apparatus, wherein the imaging device includes a first camera facing to an entire can from a direction orthogonal to an axial direction of the can and taking an image of the entire can and a second camera facing to an opening-side end portion of the can from a direction orthogonal to the axial direction of the can and taking an image of the opening-side end portion of the can, wherein whether printing is performed properly as compared with a master image is inspected, densities in designated positions for respective colors are measured by using the image taken by the first camera, and misalignment values with respect to set positions of printing misalignment inspection marks printed on the opening-side end portion of the can for respective colors are measured by using the image taken by the second camera, and wherein the conveyance device comprises: a sampling line transferring part of a number of cans printed by the can printing apparatus to the imaging device; and a return line returning the cans determined as good products in the can inspection device to a conveyance line of the can printing apparatus.
 6. The can inspection device according to claim 5, wherein the can is rotated by a rotation device, and a drive side of the rotation device and the can on the driven side are synchronized through an encoder. 